My advice? Wait for 2.0. Seriously, forget all the fanboy hype. It is stylish, but lacks configuration options and (would you believe it?) requires you to plug in your iPad to import SSH keys, which is simply ridiculous (I either generate my own in the other clients or import mine by copying/pasting via SSH itself).
Update: To my utter amazement, Prompt supports the Control key on a Bluetooth keyboard connected to an iPad freshly updated to 4.3.2. I don’t know if they’re using private APIs or if Apple has finally allowed developers to access all keycodes, but at least I’ve found a reason to use it (even though the lack of proper key management is a royal pain in the posterior).
Infuriatingly, Prompt does not support the cursor keys (but that’s not a significant issue inside vim). Let’s hope this gets sorted out soon, and that someone churns out a decent ARD client.